Sealed fissured roof surface and method therefor



W. G. CRAIG Oct. 12, 1965 SEALED FISSURED ROOF SURFACE AND METHOD THEREFOR Original Filed March 25, 1958 FIG. 2

INVENTR.

wlLLls G. CRAIG BY ma,

ATTORNEYS United States Patent O 3,210,902 SEALED FISSURED ROOF SURFACE AND METHOD THEREFOR Willis G. Craig, Willoughby, Ohio, assignor to The Lubrizol Corporation, Wicklife, Ohio, a corporation This is a division of application Serial No. 723,903, filed March 25, 1958 and now Patent No. 3,095,339.

This invention relates as indicated to a roofing element. More particularly it relates to an asphaltic roofing element which is useful in prolonging the life of a builtup roof surface. lt is useful not only in the preparation of new roof surfaces, but also in the repair of old, worn roof surfaces.

The roof surfaces of many buildings, particularly commercial and industrial buildings, consist of flat slabs of concrete, metal, wood, etc. as the principal supporting structure. These supporting slabs are covered in most instances with asphalt-saturated felts to give the roofing a uniform protective coating. The asphalt-saturated felt serves not only to seal the joints between the abutting concrete slabs, but also to eliminate the crevices of these joints vand to provide a smooth surface which will prevent the collection of water from rain and snow.

As the supporting slabs are not fastened either to each other or to their supporting understructure, but merely rest in their positions, it is apparent that they will shift their positions from time to time with any shifting of the building structure which they cover. It is apparent furthermore that such shifting of these supporting slabs will not be uniform, but that some will shift more than others. Such motion of the slabs will place a considerable stress upon that portion of the asphaltic layer immediately above the joints between any pair of slabs. This stress inevitably results in the rupture of the asphaltic surface immediately above these joints with the result that protection from the elements of weather is no longer provided by the asphaltic layer.

It is an object of the present invention to provide an improved asphaltic roof surface.

Another object of the present invention is to provide a rooting element which serves as an effective seal of crack in a roof surface f Other objects of the invention will become apparent from the following description thereof.

An effective means has been discovered whereby an asphaltic surface can be strengthened along the lines of joints between supporting slabs of the surface, which consists of a roofing element comprising in combination a first strip ofporous, asphalt-bonded fibrous mat 4 to 12 inches wide, and centered longitudinally thereunder and in facewise contact therewith a second, asphalt-impermeable strip narrower than said first strip and held in place by the surface tack of said rst strip, said second strip being characterized by a tensile strength less than that of said first strip and an adhesion to asphalt less than the cohesion of asphalt.

The porous asphalt-bonded fibrous mat is preferably a glass fibrous mat, and a particularly suitable asphaltbonded glass fibrous mat is described in U.S. 2,811,769. Such a mat may be prepared by spraying hot, discrete asphalt particles upon a water-felted mat chopped glass strands. A mat prepared in this manner is characterized by its great strength and light weight, and also by its relatively high concentration of asphalt with respect to its glass content. Other asphalt-bonded mats may 3,210,902 Patented Oct. 1-2, 1965 also be used with success; thus an asphalt-bonded Saran fiber mat is useful, so is an asphaltic mat prepared with chopped nylon strands, cotton, jute, orlon, etc., and many other synthetic fibers can be used in the preparation of mats for the purposes of this invention.

Ordinarily this first porous strip should be about 4 inches wide. This size is ideal for use in preparing new roof surfaces and also is quite applicable in repairing Worn roofing surfaces. In some cases a worn roof surface, however, may have sutliciently wide cracks in its surfaces as to require the use of a wider first strip and in some severe cases a strip 12 inches in width will be most useful.

The second strip, an asphalt-impermeable strip, narrower than the first, asphalt-bonded strip, must have a tensile strength less than that of the asphalt-bonded strip. The reason for this limitationupon the strength of the second strip is associated with its function in distributing the stresses on the upper first strip (occasioned by the shifting of the supporting slabs of the roof surface) about a wider area than that immediately over the joints between these supporting slabs.

To illustrate the invention, an asphalt-impermeable strip about 2 inches in width is placed along the joint between abutting concrete slabs of a roof surfaceand centered thereon.l Immediately above this 2-inch wide strip there is placed'a 4-inch wide strip of porous asphaltbonded glass fibrous mat. This second, asphaltic mat is centered atop the lower, narrower strip so as to overlap on each side of this narrower strip. Then the overlapping edges of the upper strip are anchored to the supporting concrete slabs by mopping a clay asphalt emulsion onto the surface of this upper strip. The asphalt-emulsion impregnates the pores of this upper strip making contact with the concrete slabs underneath the overlapping edges and dries to leavean effective seal between the concrete and the overlapping porti-ons of the asphalt-bonded glass mat. v i

The second, flexible, narrower strip, being asphaltimpermeable, prevents attachment of the center portion of the upper strip corresponding to the area of the underneath strip to the supporting roof structure. Because of this .and also because it is'weaker in terms of tensile strength than the upper first strip it allows the stresses caused by any shifting of the abutting supporting slabs to be distributed throughout the upper asphaltic strip about an area defined by the width of the lower, asphaltimpermeable strip.

The invention may be illustrated further by'reference' to the figures of the drawing. FIGURE 1 is a top view two abutting panels of a roof surface.

ting panels is defined by the numbers 1, 2, A3a and 4. The abutting panels are 9 and 10. FIGURE 2 is a cross-sectional view of the same application in which the width of the upper asphaltic strip is represented by- 13 and 14 and the width of the lower asphalt-impermeable strip is indicated by 11 and 12. The abutting panels are 15 and 16.

An important consideration in the selection of materials that can serve as the lower, narrower asphalt-impermeable strip is that this material must be one which is free to move either with respect to the supporting roof surface itself or with respect t-o the upper asphaltic strip. It is apparent that this condition must exist if the stresses caused by the movement of the supporting slabs are to be distributed about an area wider than that of the joint being covered. In some special circumstances this narrower, asphalt-impermeable strip may be such that it adheres neither to the supporting roof structure nor to the covering asphaltic mat. Ordinarily, however, this narrower strip will be adherent to one of these surfaces, and more usually this narower strip will adhere to the covering asphaltic strip.

A particularly suitable material for use as this narrower asphalt-impermeable strip is tissue paper which has been coated on one side with a thin film of polyethylene. The polyethylene film serves to prevent adhesion of the strip to the asphalt of old, worn roof surfaces, and also to prevent the combined strips from sticking to itself when it is rolled for storage purposes. Other materials which have been used with success as the asphalt-impermeable strip include tissue paper alone (for use on new roof surafces), Saran (a copolymer of 95% vinylidene chloride and 5% vinyl chloride), aluminum foil, cellophane, and -pound kraft paper.

Still other materials which have been used successfully include synthetic resins which are painted over the joint between abutting surfaces. These include polyvinyl alcohol, polyvinyl chloride, various vinyl chloride copolymers, polyvinyl acetate, GRS-type copolymers and the like. The use of such materials as this narrower, under lying strip illustrates the situation in which this strip adheres to the supporting room structure, but is free to move with respect to the upper asphaltic strip. In this situation the asphalt-impermeable strip is sufficiently iexible to move with any movement of the abutting slabs of the roof. Being non-adherent with the asphaltic strip above, this movement does not transmit any stresses to the asphaltic strip.

With respect to the situation in which the asphaltimpermeable strip adheres to the upper asphaltic strip, but does not adhere to the supporting roof structure, any movement of the abutting slabs of this room does not transmit stresses to either of the strips which overlie the slabs because the narrower, asphalt-impermeable strip is independent of any such motion.

As mentioned earlier the lower, asphalt-impermeable strip must have a tensile strength less than that of the upper, asphaltic strip. If this is not the case the lower strip will act to reinforce the upper strip and any stresses imposed upon the system will cause the upper strip to rupture along the lines which correspond to the edges of the lower reinforcing strip. It is apparent therefore that the lower strip must have a sufficiently low tensile strength that it does not act to reinforce the upper strip.

The lower, asphalt-impermeable strip should also be characterized by an adhesion to asphalt less than the cohesion of asphalt. This property enables the lower strip to become detached from the upper asphaltic strip or an asphaltic roof surface when stresses are applied to the system. A specific illustration of the invention is as follows: A 2-inch wide strip of polyethylene-coated tissue paper is placed (polyethylene side face down) atop the joint formed by abutting concrete slabs of a new roof. Immediately on top of this strip there is placed a 4-inch wide strip of an asphalt-bonded, glass fibrous mat (prepared as in U.S. 2,811,769) such that a l-inch selvage overlies each edge of the lower strip. An aqueous clay asphalt emulsion containing 48% asphalt and 2% clay is mopped on to the top layer until the pores thereof are 4 thoroughly saturated. When the emulsion has dried the overall roof then may be surfaced by any of the methods well known in the art.

It is apparent that the upper, asphaltic strip, being anchored to separate supporting slabs which are free to move with respect to each other, must be capable of elongation. Likewise, of course, the anchoring substance (the residue from the clay asphalt emulsion of the above illustration) should also have this property. For the purposes of this invention it is necessary that this upper, asphaltic strip, when anchored to a roof surface, be characterized by an elongation of at least 10% before rupture.

Other modes of applying the principles of the invention may be employed, change being made as regards the details described, provided the features stated in any of the following clairns or the equivalent of such be employed.

What is claimed is:

1. The method of sealing a crack in a roof surface which comprises the steps of applying a narrow strip of asphalt-impermeable material directly over the crack and in free movement against the roof surface on opposite sides of the crack, which strip is characterized by an adhesion to asphalt less than the cohesion of asphalt, applying over said narrow strip a wider strip of porous, tacky asphalt-bonded fibrous mat extending beyond opposite side edges of the narrow strip against the roof surface, and adhering the extended undersurfaces of the wider strip to the roof surface with an asphaltic anchoring substance.

2. A method in accordance with claim 1 characterized further in that said asphalt-bonded fibrous mat is an asphalt-bonded glass fibrous mat.

3. A method in accordance with claim 1 characterized further in that said asphalt-impermeable strip is tissue coated on one side thereof with a thin film of polyethylene.

4. A method in accordance with claim 1 characterized further in that said asphaltic anchoring substance is an aqueous clay-asphalt emulsion.

5. In a fissured roof surface in which the abutting surface edges of said fissure tend to move with ambient conditions, a roofing element positioned and asphalt anchored on such surface over such fissure comprising in combination a narrow, asphalt-impermeable strip covering the fissure and in free movement against the roof surface on opposite sides of said fissure, and centered longitudinally thereover, a wider strip of porous, tacky asphalt-bonded brous mat 4 to l2 inches wide, the undersurfaces of said wider strip extending beyond the opposite side edges of the narrow strip and asphalt anchored against the roof surface, said narrow strip being characterized by a tensile strength less than that of the wider strip, and an adhesion to asphalt less than the cohesion of asphalt.

References Cited by the Examiner UNITED STATES PATENTS 1,694,523 12/28 White 50-194 X 1,818,005 8/31 Oden 50--203 X 2,314,523 3/43 Speer 50-194 2,811,769 11/57 Craig 264-128 3,095,339 6/62 Craig 50-194 X EARL I. WITMER, Primary Examiner. JACOB L. NACKENOFF, Examiner. 

5. IN A FISSURED ROOF SURFACE IN WHICH THE ABUTTING SURFACE EDGES OF SAID FISSURE TEND TO MOVE WITH AMBIENT CONDITIONS, A ROOFING ELEMENT POSITIONED AND ASPHALT ANCHORED ON SUCH SURFACE OVER SUCH FISSURE COMPRISING IN COMBINATION A NARROW, ASPHALT-IMPERNEABLE STRIP COVERING THE FISSURE AND IN FREE MOVEMENT AGAINST THE ROOF SURFACE ON OPPOSITE SIDES OF SAID FISSURE, AND CENTERED LONGITUDINALLY THEREOVER, A WIDER STRIP OF POROUS, TACKY ASPHALT-BONDED 